Optimal storm generation for evaluation of the inundation threat: Development and application

In recent years the hazard along U.S. coastlines from inundation produced by hurricane generated storm surge has received a lot of attention. Following hurricane Katrina in 2005 there has been a renewed emphasis on producing detailed, high resolution inundation maps. The method of choice for generation of these maps is the Joint Probability Method (JPM). This method involves developing probabilistic distributions of five important hurricane parameters (i.e. intensity, size, forward speed, heading, and landfall location) based on local climatology specific to the study area. The distributions are discretized into representative values and all possible parameter combinations are simulated with a storm surge modeling system. This approach is computationally costly when high resolution; state of the art modeling systems are used. This study develops a technique that combines an optimal storm generation algorithm with multivariate interpolation to greatly reduce the number of necessary model simulations, while preserving the accuracy of the solution. The approach is first verified by comparing the inundation hazard maps produced using the interpolation technique with those produced using the actual simulations from a highly efficient numerical model. The approach is then applied to evaluate the current day and future inundation threat in Southwest Florida, and the optimal storm database is developed using a sophisticated modeling system, CH3D (Curvilinear-grid Hydrodynamics in 3D) SSMS (Storm Surge Modeling System). The current day hazard is confined mainly to coastal locations and areas near the Everglades. The future threat level varies considerably depending on the magnitude of SLR (Sea Level Rise) and changes in hurricane intensity and frequency. SLR is the dominant factor in determining the inundation hazard. The increase in hurricane intensity is generally offset by the decrease in hurricane frequency, resulting in little change in inundation hazard when SLR is not considered. In addition to determining the potential hazard to an area, the optimal storm database is used to produce high resolution forecasts for an approaching hurricane. The interpolated inundation response is combined with probabilistic descriptions of the hurricane forecast errors to obtain a high resolution probabilistic estimate of the inundation.